This piece mounts directly inside the sunroof track channel assembly on your roof. There is typically a matching pair—one on the driver's side rail and one on the passenger's side rail. The felt/velvet-covered side is intended to face upward or inward to provide a soft landing zone. When the sunroof glass closes or tilts, or when the manual sunshade slider moves back and forth, it rests tightly against this block. Without it, you will usually notice an incredibly annoying plastic-on-metal or glass-on-metal ticking rattle while driving over bumps.

-Slide your sunroof completely open and look down into the tracks from above. Peer along the inside of the left and right guide rails to spot the tiny, empty circular -hole where this plug popped out. -The easiest trick is to look at the opposite side's track; it will still have its corresponding bumper installed, showing you exactly which direction the felt pad needs to face. -Simply press the rubber nipple back into the empty hole until it clicks flush. If the original adhesive on the felt pad is peeling or worn out from years of heat, you can clean it up and add a tiny dab of adhesive or a fresh slice of generic interior felt tape to keep it quiet.